In the prior art it is well known to solder, fuse or braze articles by condensing hot saturated vapor of a heat transfer fluid thereon at atmospheric pressure. This method is described in detail in U.S. Pat. No. 30,399 which issued on Sept. 9, 1980 and is assigned to Western Electric Company and Bell Telephone Laboratories, Inc. This patent also indicates that such operations can also be accomplished at other than atmospheric pressure.
Suggestions have been made to implement such a concept by generating a body of high pressure steam in a boiler and rapidly injecting the steam into an enclosed processing vessel containing articles to be soldered. Advantageously, steam has a much higher heat transfer rate, is more stable, non-toxic and less expensive than vapor of heat transfer fluids heretofore used at atmospheric pressure. Although the suggested technique can be used to solder articles within the vessel, problems have been encountered when attempts have been made to implement such concepts.
In practice it was found that as the high pressure jet of steam enters the processing vessel it impinges on and moves small articles which are to be soldered. Additionally, the thick metal walls of the process vessel act as a large heat sink which condenses a substantial percentage of the incoming vapor thereon, leading to the establishment of large temperature variations within the process vessel resulting in a non-uniform vapor heating environment in which articles are to be soldered. The article movement and non-uniform heating of the processed article results in poor soldering quality and attendant low yield.
Accordingly, there is a need for a high pressure vapor condensation process and apparatus which provides a uniform vapor heating environment for soldering, fusing or brazing articles.